Failed Emissions/high NOx

Hey y'all,

Just tested my 99 tacoma for emissions. Everything looks ok but I failed due to high NOx.
Here are the numbers

Miles: 329382

Readings/Limits

HC GPM 0.0644/0.8000

CO GPM 1.6611/15.000

CO2 GPM 371.9083

NOx GPM 1.7376/1.5000

Of course I looked up stuff before coming here. I know that a few things can cause this. Gonna throw some sea foam in it and already have an appointment with a place to get it fixed. Anyone else have any tips or ideas? and does that low CO reading give any concern?

 

1/4 tank gas and denature alcohol. That's all I'll say. Google is your friend.

 

Has your cat ever been replaced? No CEL?

Edit: nvm, cat does not touch NOx

 

I think it may just be carbon build up. Gonna try the whole sea foam trick and see if that helps. I get a free test so I am gonna use that up and from there, take it to a mechanic. Thanks for the tips y'all

 

EGR has a lot to do with nox as well, maybe take it apart and check for carbon build up as well.